1. Field of the Invention
This invention relates to a magnetic disk drive having multiple rotary actuators; and, more particularly, to multiple actuators with reduced interactions.
2. Description of the Background Art
Disk drives using magnetic recording of digital information comprise most of the information storage in contemporary computer systems. Specific disk drives have been developed for applications ranging from small low power drives for mobile computers to high performance drives for large net-based server applications. Disk drives have at least one rotating disk with discrete concentric tracks of data. There is at least one recording head typically comprising a separate write element and read element for writing and reading the data on the tracks. The recording head is attached to a slider and the slider is attached to a suspension. The combination of the recording head, slider and suspension is called a head gimbal assembly. In addition, there is an actuator which positions the recording head on the specific track of interest. The actuator first rotates to seek the track of interest and after positioning the recording head over that track maintains the recording head in close registration to that track.
The actuators for the vast majority of disk drives utilize a rotary structure. The rotary structure comprises a rigid support member. This support member has arms for attachment to the head gimbal assemblies. This rigid support member has an axis of rotation the location of which is defined by the position of a bearing shaft. The support member has coils generally across the center of rotation from the head gimbal assemblies. These coils in conjunction with magnets placed in close proximity to them form a voice coil motor (VCM) which is used to rotate the actuator about the bearing shaft.
High performance disk drives can have two or more separate actuators mounted on a common bearing shaft. This approach has the advantage that parallel streams of data can be simultaneously processed though the recording heads on each actuator. Alternatively while one actuator is in place and the recording head on that actuator is active processing data, the other actuator can be moving to the next track of interest. This can minimize the apparent seek time of the actuator during which data cannot not be processed by the recording head.
One problem associated with multiple actuator assemblies is that the movement of one actuator induces movement or vibrations in the other actuator. Thus if one actuator is moving while the second actuator has positioned the recording head and that head is active in processing data, then the function of the recording head is compromised by vibrations caused by the first actuator. There have been attempts in the past to dampen vibrations in actuators by placing a rubber like material between the bearing shaft and the actuator. One limitation in this approach is that rigidity is sacrificed thereby degrading actuator performance. Another limitation is that many rubber like or elastomer materials tend to outgas causing contamination problems within the disk drive. Yet another limitation for elastomer materials is the tendency to creep causing longer term dimensional instability.
What is needed is a dual actuator structure which is less prone to couple vibrations from the movement of one actuator into the second actuator.
What is disclosed is a disk drive having two or more actuators wherein the actuators share a common geometrical rotation axis but are mounted on separate bearing shafts. Separate bearing shafts result in much less mechanical coupling between the actuators compared to a single common bearing shaft.
In one embodiment, the ends of the bearing shafts are mounted on an extension or attachment portion of the centrally located magnet mounting plate which supports some of the magnets of the VCM. The plate extension can be slotted for additional vibration isolation. Alternatively two separate central plates can be used for greater vibration isolation. Additionally, damping material can be used between the two plates.
In another embodiment, the separate bearing shafts are mounted independently from the magnet mounting plates.